A stereoscopic graphics display system forms on a display screen stereoscopic images that appear to have three-dimensional qualities. Such display systems can be used advantageously in association with, for example, mechanical engineering computer-aided design systems.
A stereoscopic image of an object includes a right-eye view of the object and a left-eye view of the object. The right- and left-eye views are rendered on a two-dimensional display screen and are directed to an observer's right and left eyes, respectively. The right- and left-eye views differ by a preselected amount of binocular disparity that is defined by a binocular viewing model. The binocular disparity allows the observer to perceive from the right- and left-eye views the three-dimensional qualities of the stereoscopic image.
The binocular viewing model defines a three-dimensional viewing volume within which the stereoscopic images rendered on the display screen of the stereoscopic graphics display system appear to lie. In a typical stereoscopic graphics display system, the viewing volume is employed as a single, continuous image space for displaying a single stereoscopic image. Although it can synthesize a stereoscopic image that includes image components representing several objects, such a system requires the use of relatively complex mathematical models to synthesize such multiple component stereoscopic images. The complexity of the mathematical models representing multiple component stereoscopic images causes them to be rendered relatively slowly and requires that they be re-rendered when only one image component is changed. As a result, a change in even one of the image components is also a relatively slow process.
Furthermore, in such systems all of the image components are typically rendered in accordance with the same binocular viewing model and, therefore, have the same depth characteristics. It is often useful, however, to view different stereoscopic images in accordance with different binocular viewing models.
Certain conventional text-based systems and two-dimensional graphics display systems are capable of displaying multiple images. Such systems employ a "windowed" environment in which the display screen of the system is divided into multiple two-dimensional windows that contain multiple images. The windowed environments of text-based and two-dimensional graphics display systems have, however, been difficult to implement in a stereoscopic graphics display system.
A first difficulty stems from the fact that images rendered by a stereoscopic graphics display system have depth characteristics. The abovedescribed text-based and two-dimensional systems typically allow windows to be "stacked" so that a preferred window can overlap and occlude another window on the display screen. In the stacking of windows, the preferred window typically appears to be positioned in front of the other window.
In a stereoscopic graphics display system, however, the image in the preferred window could appear to lie at a first location that is behind a second location at which the image in the other window appears to lie. Under such circumstances, an observer could perceive depth cue contradictions between the two windows such that the preferred window appears to be positioned in front of the other window but that the image in the preferred window appears to be positioned behind the image in the other window. Depth cue contradictions can cause the observer to experience eye fatigue or discomfort.
A second difficulty stems from the fact that different stereoscopic images are often rendered in accordance with different binocular viewing models that provide the images with different depth characteristics. A windowed environment in a stereoscopic graphics display system should, therefore, be adapted to provide different windows with different binocular viewing models. This differs from the rendering of the images and the windows of text-based and two-dimensional graphics systems, which are defined within the plane of the display screen.